Transcript bionic_arduino_class2

Bionic Arduino
Introduction to Microcontrollers with Arduino
Class 2
13 Nov 2007 - machineproject - Tod E.
Kurt
What’s for Today
• Random Behavior
• RGB LEDs
• Color mixing
• Analog input with variable resistors
• Potentiometers & photocells
• Basic serial input & output
• Playing sound with piezo buzzers
Recap: Blinky LED
Make sure things still work
Load “File/Sketchbook/Examples/Digital/Blink”
compile
upload
TX/RX flash
sketch runs
Known Good
Configuration
Rule #1 of experimenting:
Before trying anything new,
Get back to a known working state
So spend a few minutes & get “Blink” working again
Getting the Board Set
Up
schematic
wire up pin 9 LED too
Questions / Review
Any questions, comments, or problems?
Aside: LED Light
Tubes
Snug-fit straws
on the end of
your LEDs to
make them glow
more visibly
Random Behavior
“CandleLight”
Uses simple
pseudo random
number
generator to
mimic flame
Use random(min,max)
to pick a number between
min & max.
Analog Input
To computers, analog is chunky
Analog Input
•
•
•
Many states, not just two (HIGH/LOW)
Number of states (or values, or “bins”) is
resolution
Common computer resolutions:
•
•
•
8-bit = 256 values
16-bit = 65,536 values
32-bit = 4,294,967,296 values
Analog Input
• Arduino (ATmega168) has six ADC
inputs
• (ADC = Analog to Digital Converter)
• Reads voltage between 0 to 5 volts
• Resolution is 10-bit (1024 values)
• In other words, 5/1024 = 4.8 mV smallest
voltage change you can measure
Analog Input
Sure sure, but how to make a varying voltage?
With a potentiometer. Or just pot.
50k
+5V–
measure–
gnd–
The pot you
have
pots also look like
this
Potentiometers
Moving the knob is like moving
where the arrow taps the voltage on the resistor
What good are pots?
• Anytime you need a ranged input
•
(we’re used to knobs)
• Measure rotational position
• steering wheel, robotic joint, etc.
• But more importantly for us,
potentiometers are a good example of a
resistive sensor
Arduino Analog Input
Plug pot directly into breadboard
Two “legs” plug into +5V & Gnd
(red + & blue -) buses
Middle “post” plugs into a row
(row 7 here)
Run a wire from that row to
Analog In 2
Pot
&
LED
Circuit
This is what your board should have on it
now
In schematics, inputs are usually on the left, outputs on the right
Also, more positive voltages are on the top, more negative on the bottom
Varying Brightness by
Hand
“PotDimmer”
Turn the knob to
change LED
brightness input
process the
input data
output
Most all embedded
systems have a
input→process→output
loop
Two Ways to
Hook up LEDs
To turn ON: digitalWrite(9,HIGH)
To turn OFF: digitalWrite(9,LOW)
To set brightness: analogWrite(9,val)
To turn ON: digitalWrite(9,LOW)
To turn OFF: digitalWrite(9,HIGH)
To set brightness: analogWrite(9,255-val)
RGB LEDs
Normal LED
anode +
anode +
cathode –
cathode –
RGB LED
anode +
red cathode –
+
blue anode
cathode
green cathode
–
–
red
blue green
actually 3 LEDs in one
package
Color Mixing
With just 3 LEDs you can make any* color
With RGB you can
make any color
(except black)
Mixing light is the additive color model
(paint is subtractive color, and can give you brown)
Laying out RGB LED
Circuit
slightly bend the longest lead and plug it into the +5v (red)
bus
plug remaining leads into rows (12,14,&16 here)
connect 220 (red-red-brown) resistors across middle to matching
rows
run wires from resistors to pins 9,10,11 of Arduino, can color-code if you
want
RGB Color Fading
“RGBMoodLight”
Slow color
fading and
mixing
Also outputs the current
color values to the serial
port
Pot-controlled RGB
Pot-controlled RGB
“RGBPotMixer”
Use the pot from
before to control
the color mix
The code turns the single ranged
input value into “sectors” where
each sector is a color
Sensing the Dark
• Pots are example of a voltage divider
• Voltage divider splits a voltage in two
• Same as two resistors, but you can vary
them
Sensing the Dark:
Photocells
• aka. photoresistor,
light-dependent
resistor
• A variable resistor
• Brighter light == lower resistance
• Photocells you have range approx. 010k-1M
schematic symbol
Photocell Circuit
pin A2
brown-blackorange
gnd
Try it with RGBPotMixer from before
Mood Light
Diffuser made from
piece of plastic
scratched with
sandpaper
Resistive sensors
circuit is the same
for all these
thermistor
(temperature)
photocell
(light)
flex sensor
(bend, deflection)
force
sensors
(pressure)
also air
pressure and
others
•
•
Communicating
with Others
Arduino can use same USB cable for
programming and to talk with computers
Talking to other devices uses the
“Serial” commands
•
Serial.begin() – prepare to use serial
• Serial.print() – send data to
computer
• Serial.read() – read data from
computer
Watch the TX/RX
LEDS
• TX – sending to PC
• RX – receiving from PC
• Used when
programming or
communicating
Arduino Says “Hi”
“SerialHelloWorld”
Sends “Hello
world!” to your
computer
Click on “Serial
Monitor” button to
see output
Watch TX LED compared
to pin 13 LED
Telling Arduino What To
Do
“SerialReadBasic”
You type “H”, LED
blinks
In “Serial Monitor”,
type “H”, press Send
Serial.available() tells
you if data present to read
Arduino
Communications
is just serial communications
• Psst, Arduino doesn’t really do USB
• It really is “serial”, like old RS-232 serial
• All microcontrollers can do serial
• Not many can do USB
• Serial is easy, USB is hard
serial terminal from the olde days
Serial
Communications
• “Serial” because data is broken down into bits,
each sent one after the other down a single wire.
•
The single ASCII character ‘B’ is sent as:
‘B’ =
=
=
•
•
•
0 1 0 0 0 0 1 0
L H L L L L H L
HIGH
LOW
Toggle a pin to send data, just like blinking an LED
You could implement sending serial data with
digitalWrite() and delay()
A single data wire needed to send data. One other to
receive.
Arduino & USB-toserial
Arduino board is really two circuits
Arduino Mini
Arduino Mini separates the two circuits
Arduino Mini USB adapter
Arduino Mini
Arduino to Computer
chip
USB is totally optional for Arduino
But it makes things easier
Arduino & USB
• Since Arduino is all about serial
• And not USB,
• Interfacing to things like USB flash
drives, USB hard disks, USB webcams,
etc. is not possible
Controlling the
Computer
• Can send sensor data from Arduino to
computer with Serial.print()
• There are many different variations to
suite your needs:
Controlling the
Computer
You write one program on Arduino, one on the computer
In Arduino: read sensor, send data as byte
In Processing: read the byte, do something with it
Controlling the
Computer
• Receiving program on the computer can
be in any language that knows about
serial ports
• C/C++,
Perl, PHP, Java, Max/MSP,
Python, Visual Basic, etc.
• Pick your favorite one, write some code
for Arduino to control
Controlling Arduino,
Again
“SerialReadBlink”
Type a number 1-9
and LED blinks that
many times
Converts typed ASCII value
into usable number
Most control issues are
data conversion issues
Serial-controlled RGB
“SerialRGBLED”
Send color
commands to
Arduino
e.g. “r200”, “g50”, “b0”
Sketch parses what
you type, changes
LEDs
g50
Reading Serial Strings
•
•
•
The function
“Serial.available()”
makes reading strings
easier
Can use it to read all
available serial data
from computer
The “readSerialString()”
function at right takes a
character string and
sticks available serial
data into it
Piezoelectrics
• Big word – piezein is greek for “squeeze”
• Some crystals, when squeezed, make a
spark
• Turns out the process goes the other way
too
• Spark a quartz crystal, and it flexes
• Piezo buzzers use this to make sound
(flex something back and forth, it moves air)
Piezo Buzzers
•
•
•
Two wires, red & black.
Polarity matters:
black=ground
Apply an oscillating voltage
to make a noise
The buzzer case supports
the piezo element and has
resonant cavity for sound
What’s in a Piezo
Buzzer?
You can get at the
piezo element pretty
easily.
Be careful not to crack
the white disc that is
the actual piezo
Only take it out of its
case to use it as a
sensor
another $1.99 I won’t be getting back from Radio Shack
Piezo Buzzer
Play a Melody
“SoundSerial”
Play the piezo beeper
with the Serial
Monitor
Type multiple letters
from “cdefgabC” to
make melodies
Making it Quieter
Easiest way: add a resistor
Play a Stored Melody
“PlayMelody”
Plays a melody
stored in the Arduino
Could be battery-powered, play
melody on button trigger, control
playback speed with photocell,
etc.
Make a Theremin
“ooo-weee-ooooo”
The original spooky
sound machine
Works by measuring your
body’s electric field
No touching needed!
We’ll use light in lieu of RF
Leon Theremin
Light Theremin
“Theremin”
Move hand over
photocell to
change pitch
Play with val processing & cycles
count to alter sensitivity, pitch and
timbre
Other Serial Devices
to Wi-Fi
to Ethernet
to graphic LCD
to 8-servo controller
Serial Examples
to Roomba
Going Further
• Piezo buzzers
• Can hook up multiple buzzers for
polyphonic sound
• Can play waves other than just
square waves using PWM
techniques
• Can also be used as input devices
(we’ll cover that later)
Going Further
• Serial communications
• Not just for computer-to-Arduino
communications
• Many other devices speak serial
• Older keyboards & mice speak are
serial
(good for sensors!)
• Interface boards (graphic LCDs, servo
drivers, RFID readers, Ethernet, Wi-Fi)
Going Further
• RGB LEDS
• You can pretty easily
replicate the Ambient Orb
($150) functionality
• Make a status display for
your computer
• Computer-controlled
accent lighting (a wash of
color against the walls)
END Class 2
http://todbot.com/blog/bionicarduino/
Tod E. Kurt
[email protected]